Remove canonical signature check

[0xKodzy]

Duplicate of EOSIO/eos#6699

Requiring signatures to be canonical is necessary to prevent Signature Malleability attacks.
However, in Antelope-based chains, this requirement serves no functional purpose since the signature does not affect the transaction hash generation.
Consequently, even if an attacker alters the signature, they cannot exploit it.

The primary problem with canonical checks is that they require the signer to repeat the entire signing process until a canonical signature is found. This can be quite time-consuming for applications that need high-speed signing.

[spoonincode]

Replaced with AntelopeIO/spring#1106